MacOS App store not recognizing my Apple ID password
I just replaced the HD in my Mac mini (late 2012). When I installed the OS, it installed 10.8.5. In order to upgrade to Catalina, I needed to upgrade it to Yosemite, El Capitan, or Sierra first. I was able to install Sierra and in order to upgrade to Catalina, I need to install it through the App store.
The App store is asking for my Apple ID/password. I entered it, but it's saying it's incorrect even though my phone/iPad beeped asking me to verify the login. I tried typing it slowly, but same thing happened. App store complains it's wrong, but my phone/iPad beeped. I was able to sign out/sign in to iCloud in the Mac so I know the password is correct. Also, I used the same ID/password to log into this forum from a different computer. I rebooted the Mac a few times, opened/closed the App store a few times, but it's still refusing to recognize my password. What's going on? If it was incorrect, why would my phone/iPad beep?
Mac mini, OS X 10.10